Multiple target, multiple energy radioisotope production

ABSTRACT

A multiple target array for receiving particles from a particle beam generator includes a particle beam transport path having a transport inlet and a transport outlet, the inlet receiving a particle beam from the particle beam generator. A kicker magnet is positioned along the particle beam transport path. The kicker magnet has an ON state and an OFF state and a kicker magnet inlet and a kicker magnet outlet. The array further includes a plurality of target paths, each of said target paths having a target inlet and terminating in a target. One of the target inlets is connected to the transport path adjacent to the kicker magnet outlet, and the particle beam in the transport path entering the kicker magnet inlet passes along the transport path through the kicker magnet outlet when the kicker magnet is in the OFF state, and the beam is directed to the target inlet when the kicker magnet is in the ON state.

RELATED APPLICANTION

[0001] This application relies on provisional application Serial No.60/107,238, filed Nov. 5, 1998, and entitled “Multiple Target, MultipleEnergy Radioisotope Production”.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a multiple target station formultiple energy particle beam bombardment. The apparatus and method haveparticular utility in connection with radioisotope production.

[0004] 2. Description of Related Information

[0005] The use of cyclotrons and linear accelerators for radioisotopeproduction is known in the art. To produce a radioisotope, theaccelerated particle beam produced by a cyclotron or linear acceleratoris used to bombard a target.

[0006] For efficiency of production, it is desirable to simultaneouslybombard multiple targets at multiple energies. To bombard multipletargets, geometrical splitting techniques are used on the acceleratedparticle beam. One such technique known in the art employs strippingfoils, which may be configured to create electrostatic extractionchannels to split the beam. However, the use of stripping foils createslimitations: only two, or perhaps three, targets can be simultaneouslybombarded. An even greater drawback is that each individual targetstation is limited to a fixed, predetermined energy and a set fractionof the incident beam.

SUMMARY OF THE INVENTION

[0007] The present invention does not limit the number of targets thatmay be simultaneously bombarded. Additionally, each target may be usedfor the entire range of available energies. A further advantage of thepresent invention is that the fraction of the incident beam and theenergy bombarding a single target can be readily adjusted.

[0008] The present invention employs a series of magnets placed alongthe path of the particle beam to control the beam. The magnets allow thebeam to be focused, permitting the use of multiple energy levels. Themagnets also allow the pulses of a pulsed particle beam to be directedtowards individual targets on a pulse-by-pulse basis. Linearaccelerators allow for particle beam pulses, or bursts, of severalpredetermined energy levels to be generated in a particle beam path.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] For a more complete understanding of the present invention andfor further advantages thereof, reference is now made to the followingDescription of the Preferred Embodiments taken in conjunction with theaccompanying Drawings in which:

[0010]FIG. 1 depicts a particle beam transport system terminating inmultiple target areas;

[0011]FIG. 2 depicts a sequential array of linear accelerators;

[0012]FIG. 3 depicts a multiple target array; and

[0013]FIG. 4 is an expanded view of a kicker magnet, and the transportpath and target path at the kicker outlet.

DESCRIPTION OF THE PRESENT EMBODIMENT

[0014] Referring now to FIG. 1, an embodiment of a particle beamtransport system terminating in multiple target areas for a multipleenergy, multiple target linear accelerator system is therein depicted,and is generally referred to by the numeral 10. A sequential array ofparticle beam accelerators 12 provides a particle beam. Connected to thesequential array 12 is a particle beam transport tube or path 14. Thetransport path 14 is defined by a sealed, enclosed tube. The purpose ofthe sealed tubular path is to allow the particle beam to travel in avacuum along a predetermined route. A series of target paths 16 branchfrom the transport path 14. Similar to the transport paths 14, thetarget paths 16 are also sealed tubular enclosures. The target pathsterminate at targets 18. An additional target 18 is placed at thetermination of the transport path 14.

[0015] Turning now to FIG. 2, a sequential array 12 of linearaccelerator tanks 20 is depicted. In the present embodiment of theinvention, four drift tube linear accelerator tanks 20 arc placedsequentially, or end-to-end, to create the sequential array 12. In thisarrangement, the accelerator outlet 22 of one accelerator tank 20 isconnected to the accelerator inlet 24 of the next accelerator tank 20 ina series, starting at an intial accelerator tank 20 and terminating at aterminal accelerator tank 20. The drift tubes in a linear acceleratortank 20 are pulsed to create a pulsed particle beam consisting of aseries of particle bursts, or pulses. In the preferred embodiment, thepulses are output at a repetition rate of 360 Hz, which translates to abeam pulse every 2.8 milliseconds. The use of multiple linearaccelerator tanks 20 allows for particle beams of a variety of energylevels to be generated. In the present embodiment of the invention, thefirst two linear accelerator tanks 20 are powered to generate a 33 meVparticle beam. The third accelerator tank 20 may be used in conjunctionwith the first two tanks to produce a 51 meV particle beam, and all fouraccelerator tanks 20 may be used to produce a 70 meV beam. It will beapparent to those skilled in the art that different combinations ofaccelerators can be used to produce different or additional energylevels. The drift tubes in the accelerator tanks 20 can be pulsed on andoff to vary the particle beam energy level from pulse to pulse.

[0016]FIG. 3 depicts a multiple target array. The target array comprisesthe transport path 14 from the outlet 24 of the last accelerator tank20, the target paths 16 deviating from the transport path 14 and thetargets 18. The transport path 14, which is a sealed, enclosed tube 14,has a transport inlet 26 for receiving a particle beam from the particleaccelerator tanks 20 (FIG. 3). The transport inlet 26 is connected tothe accelerator outlet 24 at the termination of the sequential array 12.The transport path 14 terminates at a transport outlet 28.

[0017] A series of focusing magnets 30 are situated downstream of thetransport inlet 26 along the transport path 14. After a pulsed particlebeam produced by the sequential array 12 enters the transport path 14,the beam passes through the series of focusing magnets 30.

[0018] In the present embodiment, a series of four pulsed quadropolemagnets are used as focusing magnets 30. The magnets have a centralorifice through which the beam flows. For purposes of this invention,when a beam enters, travels or traverses, through a magnet, the point ofentry into which the beam path enters the central orifice of the magnetis referred to as an inlet, and the point at which the beam path exitsthe central orifice is referred to as an outlet. In the presentembodiment, all of the magnets are external to the transport path 14,such that the transport tube 14 passes through the central orifice ofthe magnet. The inlet and outlet nomenclature is also used when the beamenters or exits a tube or path, such as the transport path 14 or atarget path 16, and the accelerator tanks 20.

[0019] The focusing magnets 30 are used to adjust, or focus, theparticle beam. The pulsing of the focusing magnets 30 acts upon particlebeams of different energy levels traversing the set transport path 14. Adifferent magnetic field is required to properly focus the particle beamfor each different energy level of pulse. The magnetic field generatedby a focusing magnet 30 is varied by varying the current to the focusingmagnet 30 from pulse to pulse. Each quadropole magnet 30 is powered byan individual pulsed power supply, which allows the current to be variedfrom pulse to pulse.

[0020] After the particle beam pulse is focused by the focusing magnets30, the particles in the beam pulse travel further along the transportpath 14. A series of kicker magnets 32 are disposed along the transportpath 14 between the focusing magnets 30 and the transport outlet 28.Referring to FIG. 4, each kicker magnet 32 has a kicker inlet 34 throughwhich the beam enters and a kicker outlet 36 through which the beamexits. In the present embodiment, pulsed dipole magnets located atregular intervals along the path serve as kicker magnets 32. The kickermagnets 32 can be pulsed by an electrical current, placing the kickermagnet 32 in an “on” state. When the kicker magnet 32 is on, magnet 32will act upon the beam pulse traveling through the kicker magnet 32 bycausing the pulse to deviate from the transport path 14. When the pulseddipole magnet 32 is not pulsed by a current, the kicker magnet 32 is inits “off” state, and a beam traveling through the magnet is unaffected.

[0021] Target paths 16 branch, or deviate, from the transport path 14and terminate in target stations 18. A beam enters the target path 16through its target inlet 38. The target paths 16 branch off thetransport path 14; the target inlets 38 are disposed adjacent to thekicker outlet 36 of each kicker magnet 32. The transport path 14actually extends through the central orifice of the kicker magnet 32. Atthe kicker outlet 36, the transport path 14 continues, but a separatetarget path 16 deviates from the transport path 14 just after thetransport path exits the kicker outlet 14.

[0022] In the preferred embodiment, the target paths 16 deviate from thetransport path 14 at 14° angles. This angle was selected by the abilityof a kicker magnet 32 to respond to a beam pulse of maximum systemstrength, which has been given as 70 meV in the present embodiment. Itwill be apparent to those skilled in the art that a different anglecould be used for kicker magnets of different strengths or for differentmaximum beam energy levels. Because the incident angle of the targetpath 14 is fixed in the system of the present invention, the strength ofthe magnetic field produced by the kicker magnet 32 must be adjusted forthe energy level of the beam pulse, so that the beam pulse enters thetarget path 16. The variation in the strength of the magnetic fieldproduced by the kicker magnet 32 is achieved by varying the current tothe kicker magnet 32.

[0023] Returning to FIG. 3, it should be noted that for physical layoutpurposes, it is desirable to minimize the length of the transport path14 and the target paths 16 and the area between the target stations 18.The paths may be shortened, and the target stations 18 may be placedcloser to one another, by bending the target paths 16. The beam pulse issteered along the bent target path 16 through the use of a deflectingmagnet 40. In the present invention, a dipole bending magnet is used asa deflecting magnet 40. The target path 16 is bent at a 31° angle, sothe deflecting magnet 40 is energized to deflect each pulse traversingthe target path 16 at that angle to maintain a beam pulse along thetarget path 16. It will be apparent to one skilled in the art thatdifferent angles, different or additional deflecting magnets, orvariations in placement of the target stations 18 relative to thetransport path 14 could be used for different physical layouts.

[0024] In the present embodiment, a total of five kicker magnets 32 areemployed. Each of the five kicker magnets 32 can deviate a particle beaminto a target path 16 terminating in a target 18. The target inlet 38 ofan additional target path 16 is connected to the terminal outlet 28. Inthe present embodiment, a deflecting magnet 40 is not present in thetarget path 16 connected to the terminal outlet 28, in order to minimizethe length of the particular target path. The target 18 of thisparticular target path 16 may also be used as a dump station forunwanted pulses. Therefore, the described embodiment has a total of sixtargets 18. However, the number of kicker magnets 32 can be varied tovary the number of targets 18.

[0025] To allow the electrical current input to each kicker magnet 32 tobe readily adjusted, each kicker magnet 32 is powered by an individualpulsed power supply. Individual power supplies allow the current to eachkicker magnet 32 to be individually selected, so that each kicker magnet32 can be turned on and off individually. The focusing magnets 30 arealso powered by individual pulsed power supplies which allows themagnetic field of each individual focusing magnet 32 to be setindependently. Therefore, the spacing between the focusing magnets 30does not limit the system to a particular beam wavelength.

[0026] In the present invention, a computerized control system controlsthe power supply for each focusing magnet 30 and for each kicker magnet32. The power supplies ultimately control the state and the strength ofthe magnetic field output of each kicker magnet 32 or focusing magnet30. In the case of the focusing magnets 30, the control system adjuststhe current, which powers the magnets to an appropriate level for thepower of each particle beam pulse. In the case of the kicker magnets 32,the control system controls the state of each kicker magnet 32,determining whether a beam pulse is sent to the target 18 associatedwith the kicker magnet 32 or further down the transport path, as well asthe strength of the kicker magnet 32 field. For example, the controlsystem controls the pulsed power supply for the first pulsed kickermagnet 32 to output a selected current pulse, such that the pulsedmagnet reaches a proper magnetic field level to divert the desired beampulse by 14° before a desired beam pulse enters the kicker magnet 32which causes the desired beam pulse to deflect to the first targetstation 18. The current may then be controlled so that the magneticfield level in the pulsed kicker magnet 32 will return to zero (placingthe kicker magnet 32 in its “off” state) before the next beam pulsearrives. For the next pulse, when the power supply does not output apulsed current, the beam pulse will not be deflected and will travel tothe next kicker magnet 32. If the second kicker magnet 32 receives anappropriate current pulse from its power supply, the beam pulse will bedeflected to the second target station 18. If no current pulse is sentfrom the power supply of the second kicker magnet 32 to the magnet, thebeam will continue to the third kicker magnet 32.

[0027] The controller repeats the above selection process at each kickermagnet 32, thus allocating the beam pulses amongst the multiple targets18. If no kicker magnets 32 are pulsed, the beam pulse is directed to abeam dump or target 18 beyond the transport outlet 28. Different energybeams are directed to the desired target 18 by ensuring that the propermagnetic field level is produced in the kicker magnets 32.

[0028] Additions to the present invention can be employed to ensure anefficient system. For example, FODO (focusing-defocusing) quadropolemagnets may be placed along the transport path 14 to maintain the beamfocus as it traverses the transport path 14. Sensors placed along thetransport path 14 can relay data to a computerized control system.Focusing magnets in the target path 16 immediately prior to the targets18 can ensure the precision of the beam prior to its bombardment intothe target 18. These magnets are set to bend and focus the desiredoutput beam pulse.

[0029] While a preferred embodiment of the a particle beam transportsystem terminating in multiple target areas has been described indetail, it should be apparent that modifications and variations theretoare possible, all of which fall within the true spirit and scope of theinvention. For example, the present invention may be adapted for usewith any suitable particle beam accelerator; a different number ofaccelerators could be used for a different number of energy levels; andthe multiple energy levels could be achieved by funneling the output ofmultiple particle beam accelerators with deflecting magnets rather thanusing sequential placement. Different types of beam path energizers maybe substituted for the magnets. The controller may consist of amicroprocessor or other computerized devices. Additionally, differentconfigurations of magnets can be used to allow for additional targetareas.

[0030] Whereas the present invention has been described with respect tospecific embodiments thereof, it will be understood that various changesand modifications will be suggested to one skilled in the art and it isintended to encompass such changes and modifications as fall within thescope of the appended claims.

What is claimed is:
 1. A multiple target array for receiving particlesfrom a particle beam generator comprising: a particle beam transportpath having a transport inlet and a transport outlet, said inletreceiving a particle beam from the particle beam generator; a kickermagnet positioned along said particle beam transport path, said kickermagnet having an ON state and an OFF state and a kicker magnet inlet anda kicker magnet outlet; a plurality of target paths, each of said targetpaths having a target inlet and terminating in a target; wherein one ofsaid target inlets is connected to said transport path adjacent to saidkicker magnet outlet, and wherein the particle beam in said transportpath entering said kicker magnet inlet passes along said transport paththrough said kicker magnet outlet when said kicker magnet is in the OFFstate, and said beam is directed to said target inlet when said kickermagnet is in said ON state.
 2. The multiple target array of claim 1further comprising a plurality of kicker magnets disposed along saidparticle beam transport path and wherein one of said plurality of targetinlets are connected to said transport path adjacent to one of saidplurality of kicker magnets outlets.
 3. The multiple target array ofclaim 2 further comprising a deflecting magnet disposed in each of saidplurality of target paths for deflecting the beam in said target path,thereby allowing a bend in said target path.
 4. The multiple targetarray of claim 1 further comprising a plurality of particle beamaccelerators.
 5. The multiple target array of claim 4 wherein saidplurality of particle beam accelerators comprise linear acceleratorspositioned in a sequential array.
 6. The multiple target array of claim1 further comprising a plurality of focusing magnets in said transportpath positioned between the particle beam generator and said kickermagnet.
 7. An apparatus for producing particle beams at multiple energylevels comprising a plurality of linear accelerators, each of saidplurality of linear accelerators having an accelerator inlet and anaccelerator outlet wherein said plurality of linear accelerators arepositioned with an accelerator outlet of one linear acceleratorconnected to an accelerator outlet of a next linear accelerator tocreate a sequential array.
 8. The apparatus of claim 7 furthercomprising: a particle beam transport path having a transport inlet anda transport outlet, said inlet connected to one of said acceleratoroutlets at a termination of said sequential array; a plurality of targetpaths, each of said target paths having a target inlet and terminationin a target; a plurality of kicker magnets positioned adjacent to saidparticle beam transport path, each of said plurality of kicker magnetshaving an ON state and an OFF state and a kicker magnet inlet and akicker magnet outlet; wherein each of said plurality of target inlets isconnected to said transport path adjacent to a corresponding kickermagnet outlet and said transport outlet is connected to one of saidtarget inlets, and wherein each of said kicker magnet inlets receivessaid beams, passes said beams through said kicker magnet outlet alongsaid transport path when said kicker magnet is in the OFF state, andredirects said beam to said target inlet when said kicker magnet is insaid ON state.
 9. The multiple target array of claim 8 furthercomprising a plurality of focusing magnets in said transport pathpositioned between said sequential array of said particle beamaccelerators and plurality of kicker magnets.
 10. The multiple targetarray of claim 9 further comprising a deflecting magnet disposed in eachof said plurality of target paths for deflecting the beam in said targetpath, thereby allowing a bend in said target path.
 11. A particle beamtransport system comprising: a sequential array of particle beamaccelerators having an array beam outlet; a particle beam transport pathhaving a transport inlet and a transport outlet, said inlet connected tosaid array beam outlet for receiving a particle beam; a plurality offocusing magnets on said particle beam transport path; a plurality oftarget paths, each having a target inlet and terminating in a target; aplurality of kicker magnets disposed along said particle beam transportpath, each of said plurality of kicker magnets having an ON state and anOFF state and a kicker magnet inlet and a kicker magnet outlet; whereinone of said target inlets is connected to said transport path adjacentto a one of said kicker magnet outlets, said transport outlet isconnected to one of said target inlets, said focusing magnets focus saidbeam for said plurality of kicker magnet inlets, and each of saidplurality of kicker magnet inlets receives said beam, passes said beamthrough said kicker magnet outlet along said transport path when saidkicker magnet is in the OFF state, and directs said beam to said tartetinlet when said kicker magnet is in said ON state.
 12. The system ofclaim 11 further comprising a plurality of pulsed power supplies,wherein one of said kicker magnets and one of said focusing magnets ispowered by one of said pulsed power supplies.
 13. The system of claim 12further comprising a controller for controlling said plurality of pulsedpower supplies.
 14. The system of claim 13 further wherein said each ofsaid plurality of kicker magnets comprises pulsed dipole magnets. 15.The system of claim 14 wherein said each of said plurality of focusingmagnets comprises quadropole magnets.
 16. The system of claim 15 furthercomprising a deflecting magnet disposed in each of said plurality oftarget paths to deflect said beam in said target path, thereby allowinga bend in said target path.
 17. The system of claim 16 wherein each ofsaid plurality of deflecting magnets comprises dipole magnets.
 18. Amethod of producing multiple radioisotopes from alternative pulses of aparticle beam comprising: producing a pulsed particle beam of discretepulses at a preselected energy level for each pulse; directing each ofthe pulses along a defined transport path having alternative targetbranches, wherein each of the alternative target branches terminates ina target where radioisotopes are produced; and directing a selection ofthe pulses on the transport path into an alternative target branch usingpulsed kicker magnets disposed on the transport path.
 19. The method ofclaim 18 further comprising deflecting the pulses traversing the targetbranches to follow bends in the target branches.
 20. The method of claim19 further comprising focusing each pulse as it traverses the transportpath.